Guide for attachment to a roof bolter to allow for core drilling

ABSTRACT

The present disclosure provides a coring guide for converting a mine roof bolter into apparatus suitable for guiding a coring rod, or drill, into a mine roof, as well as a method for obtaining a geological core from the mine roof using the guide. The guide includes a pair of jaws, wherein each jaw has an adapter end and a pivotable end. The adapter end of each jaw includes a cavity that faces a cavity included in the adapter end of the other jaw, such that the closed jaws form at least a major portion of a cylindrical coring cavity that accommodates a coring rod. Each jaw includes means for fixing the rod guide within a mine roof bolter apparatus such that when the coring guide is positioned between the jaws and the jaws are partially closed such that they enclose the coring rod, the roof bolter causes the coring rod to penetrate the mine roof and obtain a core sample. The method of obtaining the geological core includes installing the rod guide into the roof bolter apparatus, introducing a cylindrical coring rod, driving the coring rod into the mine roof sufficiently to accumulate a core therein, and withdrawing the rod.

FIELD OF THE INVENTION

[0001] This disclosure relates to a novel adapter (i.e., guide or chuck)for use in a mine roof bolting apparatus that permits conversion of theroof bolter into core drilling apparatus. The disclosure also relates toa method of converting the bolting apparatus and obtaining a coresample.

BACKGROUND

[0002] Underground mining machinery includes specialized apparatusadapted to carry out the operations required for obtaining the desiredmaterials from the earth while maintaining mine integrity and safety.These include longwall mining systems, continuous mining machines,loader machines, face-haulage vehicles, roof or rock, bolters, andcomparable mining vehicles and equipment.

[0003] Currently there are about 2,000 underground mines operating inthe United States, including about 1,200 to 1,400 coal mines, about 500to 600 mineral mines, and about 100 stone mines. In all undergroundmines, roof bolting is an operation that is essential in maintaining theintegrity of a horizontal mine, helping to keep the roof of the minefrom collapsing after material has been excavated from the mine face.The safety of the miners working in the mine environment thereby isenhanced. After material has been removed from the face of the mine,bolts are inserted and set into the roof of the mine to keep the rooffrom collapsing onto the workers. In order to improve safety, somemining machines have integrated the roof bolting apparatus intocontinuous mining machines, thereby reducing the risk of roof collapse.Since roof bolting is one of the most dangerous operations inunderground mining, roof bolters that work ahead of the continuousmining machines are being developed. These pre-mining bolters drill intothe seam to be mined and insert bolts at this early stage, therebygreatly reducing the risk of roof collapse. These newer roof bolterunits may incorporate contemporary robotics technology.

[0004] U.S. Pat. No. 4,158,520 discloses a rock bolting apparatus inwhich a rock drill and a rock bolt setting device are interchangeable ona single elongated guide of a feed beam. When the rock drill is inoperative position on the feed beam, the bolt setting device hangs onthe side of the feed beam, and vice versa.

[0005] U.S. Pat. No. 4,420,277 discloses a mobile integrated apparatusfor bolting the roof of an underground mine. The apparatus includes amobile frame, a boom extending from the frame, and a housing provided atthe end of the frame. The housing supports a drilling mechanismincluding a drill centralizer having a central bore therethrough and apassageway in communication with the central bore, a device fordelivering a container of roof bolting anchoring media through thepassageway, through the drill centralizer, and into a drilled hole, adevice for indexing a roof bolt into alignment with the drilled hole anda spinner for driving the roof bolt into the drilled hole.

[0006] U.S. Pat. No. 4,759,888 discloses a means and method related toautomatically installing full length grouted bolts as well as tensionedgrouted bolts, which ensures proper shredding of the grout package, andproper mixing and curing of the grout. The inventive means furtherallows control of the depth of holes drilled for rock bolting andautomatic freeing of drill steels.

[0007] U.S. Pat. No. 4,740,037 discloses a continuous mining machineincluding several components involved in cutting and conveying minedmaterial, as well as a roof bolter. As a subframe is moved away from amain frame, the bolter is operated simultaneously with cutting toperform roof bolting operations close to the face of the mine.

[0008] U.S. Pat. No. 4,702,328 discloses a mine roof-drilling systemincluding a lower surface of a retainer fixed to the drill head with anaperture formed therein to define a bearing surface for utilizing thedrill head itself to pull the assemblage of drill steel from a completedbore.

[0009] U.S. Pat. No. 4,398,850 discloses a roof bolter and process forresin bolting a mine roof. Using two positions, the bolter drills andinserts resin in one position, and inserts a bolt in a second position.The invention also includes a device designed for attachment to athree-position resin type roof bolter to convert it into a two-positionresin type roof bolter.

[0010] Much information relating to the strength and stability, orconversely, the weakness and instability, of strata that may overlay anewly-created mine roof, may be gleaned by an examination of thestratified geological structures present above the mine roof. Forexample, examination of such stratification could provide information toguide mine operators relating to the number of roof bolts required for aparticular mine roof, as well as the lengths of roof or rocks bolts thatmay be required. Currently, such information is not obtained during theroof bolting and development stages.

[0011] There is therefore a need for providing a means of readilyobtaining core samples from the roof of an advancing mine. There isfurthermore a need for minimizing the number of pieces of equipmentneeded to carry out such coring operations, since the space available inadvancing mine development areas is severely limited. Provision of amodular apparatus that could be used for both roof bolting and roofcoring operations would be greatly advantageous. The present disclosurerecognizes these needs.

SUMMARY OF THE DISCLOSURE

[0012] The present disclosure provides a guide, or adapter, forconverting a mine roof bolter into an apparatus suitable for guiding acoring rod, or drill, into a mine roof and obtaining a core sample.Information from such core samples can be used to evaluate the roofstructure and more accurately determine mine bolt placement.

[0013] The guide may include a pair of jaws, each jaw having an adapterend and a pivotable end, with the pivotable end of each jaw beingpivotally coupled to the pivotable end of the other jaw, means yieldablybiasing the jaws to an open position with respect to each other, and theadapter end of each jaw includes a jaw cavity that faces the jaw cavityincluded in the adapter end of the other jaw, with each jaw cavityhaving a cross section that forms an arc of a circle with a centralaxis, wherein when the jaws are closed to a maximal extent, the jawcavities form between them at least a major portion of a cylindricalcoring cavity in which the central axes of the jaw cavities are disposedsubstantially on a common cylinder axis, the coring cavity having acavity cylinder diameter substantially equal to the coring diameter, andadapted to enclose or grasp a coring rod, or drill, therein. In oneembodiment, each jaw includes means for holding the rod guide within themine roof bolter such that, when the coring rod is positioned betweenthe jaws and the jaws are closed such that they enclose or grasp therod, the roof bolter may engage the coring rod causing it to penetratethe mine roof and obtain a core sample, thereby converting the mine roofbolter into a mine roof coring apparatus.

[0014] In a preferred embodiment of the rod guide, the means to bias thejaws to an open position with respect to each other includes at leastone spring element having two ends, with one end coupled to one of thejaws and the other end coupled to the other jaw, and operable toyieldably bias the jaws toward maintaining the jaws in a position openedto an extent sufficient to permit a coring rod to be placed between thejaws.

[0015] In an additional preferred embodiment, means for fixing the rodguide within the mine roof bolter may be one or more tabs or projectionsthat match a receiving recess in the mine roof bolter.

[0016] In another aspect, a method of obtaining a core sample from amine roof is disclosed. The method includes the steps of providing acoring rod guide adapter having a pair of opposed jaws having jawcavities therein which together define a cylindrical coring cavityhaving a diameter substantially equal to a coring diameter, and placingthe rod guide within a pair of guide members, inserting a coring rodinto the coring rod guide such that the rod guide grasps or encloses thecoring rod, engaging the coring rod with means for impelling the coringrod into the mine roof, causing the roof bolting apparatus to impel thecoring rod into the mine roof, and withdrawing the coring rod with acore sample contained therein from the mine roof thereby obtaining acore sample.

[0017] The present disclousre is mainly directed to obtaining coresamples from mine roofs in order to obtain information and dataregarding the structure of the overlying strata and to determine boltingstrategies to provide a safe work environment. Of course, as thoseskilled in the art will realize, the rod guides and methods of thisdisclosure can also be used in other drilling and core samplingapplications such as, for example, rib or mine wall drilling, long holedrilling, and the like. In these applications, the rod guide would beused in the same manner as for roof bolting except that the drillingangle of the rock or roof bolter would be modified as appropriate. Forpurposes of this disclosure, reference to mine roofs, roof bolting, roofcoring, and the like is intended to also include these alternativedrilling/coring and applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a sectional view of a mine illustrating schematically amachine used for drilling and inserting roof bolts.

[0019]FIG. 2 is an enlarged perspective view taken generally in theregion noted 2 in FIG. 1, of a pair of guide members which might be usedin the machine, illustrating the guide members opened to receive a rockdrill or roof bolt therebetween.

[0020]FIG. 3 is a perspective view of a coring rod guide assemblyaccording to an embodiment of the present disclosure with the jawsthereof opened.

[0021]FIG. 4 shows the coring rod guide assembly of FIG. 3 with the jawsclosed.

[0022]FIG. 5 is a top plan view of the coring rod guide received in theguide members of the bolting machine with the jaws spread to receive acoring rod.

[0023]FIG. 6 is a top plan view similar to FIG. 5 with the jaws closedabout a coring rod.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0024] Referring to FIG. 1, a typical roof drilling machine is depictedgenerally at 10. The machine is illustrated operating in a mine 20 nearthe mine face 22. The machine is operable to drill holes into the roofof the mine and insert roof bolts, or rock bolts, as indicated generallyat 24 to stabilize, or secure, the roof 26 of the mine.

[0025] Machine 10 has a forwardly mounted mast 30 on which is mounted anupper pair of guide members, or jaws, 32 to hold and guide an elongaterock drill shaft indicated generally at 34. At the lower end of mast 30is a driving mechanism 36 to which the lower end of rock drill 34 iscoupled to produce rotational driving of the rock drill. The rock drillis driven upwardly and rotated to drill a hole into roof 26 into which aroof bolt 24 then may be inserted. The roof bolts also are gripped andguided by guide members 32 for driving into the roof as illustrated forpreviously installed bolts 24.

[0026]FIG. 2 illustrates a larger perspective view of examples of guidemembers 32 such as may be used on the roof bolter, which are operable toreceive and guide rock drill 34 and roof bolts 24. A rod section of arock drill 34 is illustrated generally in FIG. 2. Such would have adiameter of approximately one inch (2.54 cm).

[0027] The guide members shown here as 32 a, 32 b in FIG. 2 aresubstantially mirror images of each other. Thus the general structure ofone will be described, with the understanding that such structure issimilar for the other. Also it should be recognized that the structureof the guide members described here is merely exemplary of guide memberswhich may be used in a machine such as that noted at 10. Other forms ofguide members with which the core drilling adapter may be used maydiffer in overall configuration from those illustrated at 32 a, 32 b.

[0028] Referring to guide member 32 a, it is a rather substantial formedmember having a vertically disposed semi-cylindrical guide cavity 40formed therein adjacent the outer end of member 32 a. Progressingrearwardly (toward the viewer in FIG. 2) the inner surface 42 has asomewhat arcuate concave sweeping configuration which has a horizontallydisposed arcuate recess 44 formed therein with a lower ledge 44 a.

[0029] Guide members 32 a, 32 b are mounted for shifting toward and awayfrom each other under the influence of powered operating mechanism. Inthe illustrated embodiment the guide members are pivotallyinterconnected by a pivot pin 38. The operating mechanism may be in theform of hydraulic rams such as those indicated at 46, 48 connected toguide members 32 a, 32 b, respectively. Retraction of rams 46, 48 swingsguide members 32 a, 32 b away from each other to the positionillustrated in FIG. 2 to receive a rock drill or roof bolt withincavities 40. As the rams are extended, the guide members 32 a, 32 b aremoved toward each other whereby their cavities 40 encircle the rockdrill or roof bolt. For rotational driving of a rod, the guide members32 a, 32 b are not closed tightly about the rod, but instead are heldloosely thereabout to provide a substantially cylindrical guide whichallows the rod to rotate therein under the actuation of drive mechanism36 to which the bottom end of the rod is coupled.

[0030] Should it be desired to firmly grip, or grasp, a rod, such as forpulling it from a hole or for driving it into a hole, rams 46, 48 areextended further to clamp the guide members 32 a, 32 b tightly againstthe rod so that it is firmly and frictionally held therein.

[0031] As previously discussed, it may be advantageous to take coringsamples of the material strata in the roof of the mine to determineoptimal roof bolting conditions. The present disclosure provides anadapter for converting the mine roof bolter as described into apparatusadapted for operating a coring rod, or drill, to obtain core samplesusing the same primary machine indicated generally at 10. In this way,the same machine and operator may perform the combined tasks ofdrilling, setting roof bolts, and taking core samples.

[0032] A core drill adapter, or coring rod guide for converting a mineroof bolter into apparatus adapted for guiding a coring rod (alsoreferred to as a coring barrel assembly) into a mine roof is showngenerally in FIGS. 3 and 4 at 50. The coring rod guide includes two jaws52, 54 which are essentially mirror images of each other. Each jaw hasan outer end 52 a, 54 a and an inner end 52 b, 54 b adjacent which thetwo jaws are pivotably coupled to one another.

[0033] There are furthermore means provided in the assembly foryieldably biasing the jaws toward a position that is opened, that is inwhich the outer ends of the jaws are separated from one another by alarge gap as in FIG. 3. In the embodiment shown, the biasing means arecoil springs 60 resting in recesses 62 provided in each jaw. In FIG. 3one spring is shown attached to jaws 52, 54 and the other is illustratedready for attachment. Each coil spring has two elongate ends 60 a, 60 b,one of which is inserted into a receiving hole 66 bored into one jaw,and the second of which is inserted into a corresponding receiving hole68 of the other jaw. The resting position of the two spring ends issufficiently open that, when the spring arms are inserted into thereceiving holes in the jaws, and the jaws are moved toward each otherfrom the positions illustrated in FIG. 3, the jaws are yieldably biasedtoward opening to a considerable extent.

[0034] The outer, or adapter, end portion of each jaw 52 a, 54 aincludes structure that defines a concave jaw cavity, or void region, 72a, 72 b intended to receive a coring rod which has a larger diameterthan the previously described rock drill or roof bolt shaft. The cavityin each jaw has a cross section that forms an arc of a circle. Thecavity 72 a in one jaw faces the corresponding mirror image cavity 72 bincluded in the adapter end of the other jaw. The centers of each circleof arc substantially coincide in the mirror plane between the jaws suchthat, when the jaws are closed to a maximal extent, the coring rodreceiving, or coring, cavity 76 formed between the adapter ends of theclosed jaws forms at least a major portion of a cylindrical cavity 76with a common cylinder axis “A.” The cavity has a cavity cylinder radius“R.” Since the cylinder axis identified using the circle of arc of onejaw coincides with the axis defined using the second jaw, the entirecavity present when the jaws are closed is defined by a surface made bythe two jaws that is at least a major portion of a single cylinder.

[0035] Suitable materials of construction for the guide are standardcarbon steels or alloy steels which are readily machinable. Compositematerials also may be used if highly resistant to impact and wear.Advanced composite fabrics in a laminate can also be used if desired.

[0036] The outer sides 52 c, 54 c of jaws 52, 54 have arcuateconfigurations conforming generally to portions of the arcuateconfigurations of inner surfaces 42 of the guide members. Further,protruding tabs, ridges, or projections, 80 extending horizontally andoutwardly from surfaces 52 c, 54 c are positioned and configured to bereceived in recesses 44 in guide members 32 a, 32 b. When tabs 80 arereceived in recesses 44 the undersides of the tabs are supported onledges 44 a in the recesses.

[0037] The outer ends of sides 52 c, 54 c have arcuate recessesindicated generally at 84 adapted to receive cylindrical rod-shapedtabs, or projections, 86. A pair of holes 88 extend through eachrod-shaped tab 86 through which a pair of screws 90 extend to bereceived in threaded bores 92 in recesses 84. Rod shaped tabs 86 have aradius similar to the radius of guide cavities 40 in guide members 32 a,32 b and are positioned such that jaws 52, 54 may rest within guidemembers 32 a, 32 b with tabs 80 received in recesses 44 and tabs 86received in cavities 40. These tabs serve as means for fixing, orholding, the coring drill rod guide within a mine roof bolter apparatus.Although the tabs, recesses, and cavities shown serve this function verywell, it should be understood that other means for releasably fixing orholding the adapter in the guide members of the drilling apparatus alsocould be used.

[0038] To affix the coring rod guide to the roof bolter apparatus, guidemembers 32 a, 32 b are swung apart by retraction of rams 46, 48. Jaws52, 54 are swung toward each other to assume a position similar to thatillustrated in FIG. 4 and inserted into the position between guidemembers 32 a, 32 b. When tabs 80 on opposite side of the coring drillguide are aligned with recesses 44 in the guide members and tabs, orprojections, 86 are aligned generally with cavities 40 the force holdingthe jaws together against the yieldable biasing of springs 60 isreleased and the jaws are allowed to be swung apart under the action ofsprings 60 with tabs 80 entering recesses 44 and tabs, or projections,86 entering cavities 40. The coring rod guide thus will be held withinguide members 32 a, 32 b. This is shown in FIG. 5.

[0039] With guide members 32 a, 32 b spread widely enough apart to allowjaws 52, 54 to be spread apart as shown in FIG. 5, a hollow cylindricalcoring rod, or coring barrel assembly, 100 may be inserted into thespace between jaw cavities 72 a, 72 b. Extension of rams 46, 48 swingsguide members 32 a, 32 b and jaw members 52, 54 toward each other to theposition illustrated in FIG. 6 with the coring rod held between the twohalf-cylindrical jaw cavities 72 a, 72 b formed by each of the jaws.When the jaws are partially closed and the coring rod is held within thecylindrical cavity 76 formed between the jaws, the jaws enclose thecoring rod, such that the coring rod may rotate within cavity 76. Inthis operation rams 46, 48 are not extended to clamp the jaws tightlyagainst the coring rod. Instead, they leave the jaws of the coring rodguide somewhat loose on the coring rod to allow it to rotate therein.When the rams 46, 48 are extended further, they clamp tightly about thecoring rod 100 to grasp it frictionally and tightly therein.

[0040] The geometry of the coring rod guide is such that when a coringrod 100 is held within the grasp of the guide its centerline is close tothe centerline that a drill rod such as 34 in FIG. 2 would occupy whenthe guide members 32 a, 32 b are closed on the smaller diameter rod.Thus the lower end of coring rod 100 rests adjacent and in operativeposition over driving mechanism 36 and may be coupled thereto fordriving. When the coring rod is coupled to the driving mechanism andloosely held in the jaws, it may be rotated and driven upwardly to drillinto the overlying strata.

[0041] The coring rod has a cylindrical rod radius which is essentiallythe same as the cavity cylinder radius R. In general the coring rodradius, and therefore the cavity radius R, may be from about 1.25 toabout 2 inches or 3.175 to 5.1 cm (a diameter of 2.5 to 4 inches or 6.35to 10.15 cm) and preferably from about 1.25 to about 1.5 inches or 3.175to 3.8 cm (a diameter of about 2.5 to 3 inches or 6.35 to 7.6 cm). Inaddition, the height of each jaw, in the direction of the cylinder axis,may be from about 1 to about 4 inches or 2.54 to 10.15 cm, andpreferably from about 2 to about 3 inches or 5.1 to 7.6 cm. It should beunderstood, however, that dimensions larger or smaller than these may beused and in some cases may be appropriate.

[0042] In operation, a roof bolter apparatus is fitted with a modularchuck or guide suitable for guiding a drilling steel and/or a bolt intoa region of the mine roof. This modular chuck or guide is not requiredto be removed from the bolter apparatus in order to allow affixing thecoring rod guide. The coring rod guide, or adapter, 50 is compressed andfitted in the modular drilling or bolting chuck 32. For example, thetabs 80, 86 on the jaws that match receiving recesses in the guidemembers 32 a, 32 b are employed to orient and fix the coring rod guideto the roof bolting apparatus. Since the rod-shaped tabs 86 arereplaceable due to screw connectors 90, they may be replaced with tabsof different configuration if needed. Tabs 80 also might be madereplaceable. Of course, the coring rod guide, or adapter, 50 can bedesigned to replace the modular chuck or guide.

[0043] Once in place, the jaws 52, 54 of the coring rod guide arepermitted to flex to an open position under the influence of theopen-biasing means, such as the coil springs 60, emplaced between andjoining the two jaws to each other. Suitable means or mechanismsresident in the roof bolting apparatus are concurrently opened orrelaxed, such that the jaws of the coring rod guide open to aconsiderable extent.

[0044] In this opened configuration, as shown in FIG. 5, a hollow coringrod, or coring barrel assembly, 100 is positioned in the cavity spacebetween the opened jaws. At this time, or at a time after the jawsenclose the coring rod, the coring rod is coupled to the drivingmechanism 36 which, when operated, drives the coring rod into the mineroof. The jaws are moved to a closed position, using force generated bythe roof bolting apparatus countering the opening bias provided, forexample, by the spring coils 60, thereby forming the cylindrical cavity76 between the jaws 52, 54 at their adapter ends 52 a, 54 a. Since thecylindrical radius of the cavity and the cylindrical radius of thecoring rod are essentially identical, the coring rod is eithersurrounded loosely by or grasped tightly within the cavity depending onthe extent to which the jaws 52, 54 are closed.

[0045] With the coring rod loosely held and guided by jaws 52, 54, thedriving mechanism coupled to the coring rod may be activated. Themechanism causes the coring rod to turn on its axis as well as toadvance into the mine roof. As the coring rod advances into the strataabove the roof, and since it is hollow, a core accumulates within thecoring rod that reflects the stratification of the geological layersthat reside above the mine roof The orientation of the strata in theearth is maintained within the coring rod. This differs significantlyfrom prior art mine roof bolting apparatus, in which earth displacedfrom holes being drilled for bolting is removed and deposited in aremote area with no regard for maintaining its original stratification.

[0046] After the coring rod has advanced a suitable distance, such as adistance from about 2 feet, up to about 5 feet or 6 feet, for example,the coring rod is withdrawn, using a pulling or retracting force appliedby the driving mechanism. To do this the jaws 52, 54 are clamped againstthe coring rod to tightly and frictionally hold it in the jaws. In thisway the coring rod with the stratified core within is freed from themine roof. At this juncture the core is extracted, examined, andanalyzed in order to obtain comprehensive information related to thegeological stratification above the mine roof. This information providessignificant assistance in planning and implementing subsequent roofbolting operations in the vicinity of the core. Such cores are obtainedas often as needed as the mine advances into the earth.

[0047] The coring rod guide provides an adapter unit which may bequickly and easily attached to a roof bolting machine to convert theroof bolter from its normal roof bolt drilling and setting procedureusing a smaller diameter rod and bolts, to permit the taking of coresamples with a larger diameter hollow cylindrical coring rod. In suchoperation, the same roof bolting machine may be used in the same generallocation in which it is already operating for producing roof bolting.Minimal time is required for converting from a roof bolting to a coredrilling operation whereby it is convenient for operators to obtaininformation necessary to provide effective roof bolting.

[0048] While a preferred embodiment has been set out herein, it shouldbe apparent to those skilled in the art that variations andmodifications are possible without departing from the spirit of theinvention.

I claim:
 1. A guide for converting a mine roof bolter having a pair ofguide members mounted for shifting toward and away from each other toreceive and guide a drill rod or bolt of a selected diameter into a mineroof coring apparatus suitable for receiving and guiding a coring rodhaving a coring diameter greater than said selected diameter, said guidecomprising a pair of jaws, each jaw having an adapter end and a pivotend, with the pivot end of each jaw being pivotally coupled to the pivotend of the other jaw, means coupled to the jaws operable to yieldablybias the jaws to an open position with respect to each other, theadapter end of each jaw includes a jaw cavity that faces the jaw cavityincluded in the adapter end of the other jaw with each jaw cavity havinga cross section that forms an arc of a circle with a central axis,wherein when the jaws are closed to a maximal extent, the jaw cavitiesform between them at least a major portion of a cylindrical coringcavity in which the central axes of the jaw cavities are disposedsubstantially on a common cylinder axis, the coring cavity having acavity cylinder diameter substantially equal to said coring diameter,the pair of jaws being pivotable to an open position in which acylindrical coring rod may be disposed between the jaws at their adapterends, the jaws being pivotable to a closed position such that acylindrical coring rod placed within the coring cavity is enclosed orgrasped, and each jaw includes means for holding the guide within themine roof bolter such that when the coring rod is positioned between thejaws and the jaws are closed such that they enclose or grasp the rod,the roof bolter may engage the coring rod causing it to penetrate themine roof and obtain a core sample, thereby converting the mine roofbolter into a mine roof coring apparatus.
 2. The guide of claim 1,wherein said means to bias the jaws to an open position comprises atleast one spring element having two ends, with one end coupled to one ofsaid jaws and the other end is coupled to the other of said jaws.
 3. Theguide of claim 2, wherein the said spring element comprises a coilspring having two ends, wherein one end rests within a spring endreceptacle encompassed within one jaw and the other spring end restswithin a spring end receptacle encompassed within the other jaw, and thespring element is biased toward maintaining the jaws in an openposition.
 4. The guide of claim 1, wherein the means for holding the rodguide within the mine roof bolter comprises a tab on a jaw configured tobe received in a recess in a guide member of the mine roof bolter. 5.The rod guide of claim 4, wherein said tab and recess extendsubstantially horizontal.
 6. The guide of claim 1, wherein a roof bolterguide member has a recess formed therein for receiving a drill rod orbolt and said means for holding the rod guide within the mine roofbolter comprises a projection configured to be received in said recess.7. The guide of claim 6, wherein said projection comprises a projectionmember removably coupled to one of said jaws.
 8. The guide of claim 7,wherein said projection member is replaceable to permit adapting saidrod guide to operate with guide members of differing configurations. 9.The guide of claim 1, wherein a roof bolter guide member has a firsthorizontally disposed recess formed therein and a second verticallydisposed recess formed therein for receiving a drill rod or bolt andsaid means for holding the rod guide within the mine roof boltercomprises a tab on a jaw configured to be received in said first recessand a projection configured to be received in said second recess. 10.The rod guide of claim 1, wherein the mine roof bolter includesmechanism for shifting said guide members toward each other under powerand said jaw cavities are so configured that when forced toward eachother toward a tightly closed position they may firmly and frictionallygrip the coring rod therebetween.
 11. The rod guide of claim 10, whereinthe operating mechanism is actuatable to permit movement of said jawsaway from said tightly closed position whereby the jaw cavities looselyenclose portions of the coring rod allowing guided rotation of thecoring drill between said jaws.
 12. A guide for converting a mine roofbolter having a pair of guide members mounted for shifting toward andaway from each other to receive and guide a drill rod or bolt of aselected diameter into a mine roof coring apparatus suitable forreceiving and guiding a coring rod having a coring diameter greater thansaid selected diameter, said guide comprising a pair of jaws, each jawhaving an adapter end and a pivot end, with the pivot end of each jawbeing pivotally coupled to the pivot end of the other jaw, means coupledto the jaws operable to yieldably bias the jaws to an open position withrespect to each other comprising at least one spring element having twoends, with one end coupled to one of said jaws and the other end iscoupled to the other of said jaws, the adapter end of each jaw includesa jaw cavity that faces the jaw cavity included in the adapter end ofthe other jaw with each jaw cavity having a cross section that forms anarc of a circle with a central axis, wherein when the jaws are closed toa maximal extent, the jaw cavities form between them at least a majorportion of a cylindrical coring cavity in which the central axes of thejaw cavities are disposed substantially on a common cylinder axis, thecoring cavity having a cavity cylinder diameter substantially equal tosaid coring diameter, the pair of jaws being pivotable to an openposition in which a cylindrical coring rod may be disposed between thejaws at their adapter ends, the jaws being pivotable to a closedposition such that a cylindrical coring rod placed within the coringcavity is enclosed or grasped, and each jaw being associated with aguide member, and a jaw and its associated guide member includecomplementary recesses and projections which interact for holding theguide within the mine roof bolter such that when the coring rod ispositioned between the jaws and the jaws are closed such that theyenclose or grasp the rod, the roof bolter may engage the coring rodcausing it to penetrate the mine roof and obtain a core sample.
 13. Theguide of claim 12, wherein the said spring element comprises a coilspring having two ends, wherein one end rests within a spring endreceptacle encompassed within one jaw and the other spring end restswithin a spring end receptacle encompassed within the other jaw, and thespring element is biased toward maintaining the jaws in an openposition.
 14. The guide of claim 12, wherein a roof bolter guide memberhas a recess formed therein for receiving a drill rod or bolt and saidmeans for holding the rod guide within the mine roof bolter comprises aprojection configured to be received in said recess.
 15. The guide ofclaim 14, wherein said projection is replaceable to permit adapting saidrod guide to operate with guide members of differing configurations. 16.The rod guide of claim 12, wherein the mine roof bolter includesoperating mechanism for shifting said guide members toward each otherunder power and said jaw cavities are so configured that when forcedtoward each other toward a tightly closed position they may firmly andfrictionally grip the coring rod therebetween, and the operatingmechanism is actuatable to permit movement of said jaws away from saidtightly closed position whereby the jaw cavities loosely encloseportions of the coring rod allowing guided rotation of the coring drillbetween said jaws.
 17. A method of obtaining a core sample from a mineroof using a mine roof bolter having a pair of guide members mounted forshifting toward and away from each other to receive and guide a drillrod or bolt of a selected first diameter, comprising the steps ofproviding a coring rod guide adapter having a pair of opposed jawshaving jaw cavities therein which together define a cylindrical coringcavity having a diameter substantially equal to a coring diameter whichis greater than the first diameter, and supporting the rod guide adapterwithin the pair of guide members, inserting a coring rod into the coringrod guide such that the rod guide supports a portion of the coring rod,engaging the coring rod with means for impelling the coring rod into themine roof, causing the roof bolting apparatus to impel the coring rodinto the mine roof, and withdrawing the coring rod with a core samplecontained therein from the mine roof thereby obtaining a core sample.18. The method of claim 17, wherein the coring rod guide comprises apair of jaws and means to yieldably bias the jaws toward an openposition with respect to each other and which further comprises the stepof forcing said jaws toward each other against the yieldable bias forceto insert the coring rod guide between the guide members and thereafterreleasing the jaws to allow them to open against inwardly facingsurfaces of the guide members.
 19. The method of claim 18, wherein eachjaw is associated with a guide member, and said jaws and guide membersare provided with complementary projections and recesses which uponinserting of the coring guide between the guide members and aligning theprojections with the recesses, interact such that the projections extendinto the recesses to hold the coring guide within the guide members. 20.The method of claim 17, wherein the jaws are mounted for shifting towardand away from each other under force, and are disposed in a firstposition to loosely enclose a coring rod to permit rod rotation forboring.
 21. The method of claim 20, wherein the jaws are shifted to asecond position against the core rod to firmly and frictionally graspthe core rod.